I. Field of the Invention
The present invention relates generally to swing-frame auxiliary axle systems for load-hauling vehicles and, more particularly, to an axle-attaching swing frame that includes a self-aligning system for attaching and re-attaching the free ends of the swing frame arms of a stowable tag axle to the tag axle carrying torque tube that automatically produces repeatable, accurate alignment between the torque tube and the swing arms.
II. Related Art
Optionally deployable, swing-frame auxiliary axle systems are well known and have long been associated with a variety of types of load-hauling vehicles, particularly those accustomed to relatively heavy time-varying loading, such as dump trucks, refuse collection vehicles and transit concrete mixers. The trucks typically include a chassis or frame, a cab and a dedicated truck body mounted on the chassis behind the cab. They also include a forward steering axle placed near the front of the cab and one or more sets of drive axles spaced behind the steering axle, the drive axles often being provided in a dual axle arrangement. The auxiliary axle systems furnish additional load carrying capacity by providing an additional axle to assist the steering and drive axles in supporting the load and in adjusting the inter-axle distance or increasing the overall front-to-rear axle span distance for the vehicle. In this manner, not only does the tag axle system assist in balancing the load carried by, for example, a transit mixing cement truck, but generally it also enables the truck to carry a higher legal total payload than would otherwise be permitted because weight restrictions placed on vehicles traveling over highways are typically measured in terms of load per axle in combination with overall spacing between the vehicle axles.
Examples of such auxiliary axle assemblies that can be selectively engaged with the ground are shown, for example, in U.S. Pat. Nos. 5,897,123 and 5,018,755. Thus, it is known to have tag axle systems generally consisting of a rear tubular cross member or torque tube carrying spaced wheel assemblies, the torque tube being fixed in transverse relation to and carried by and at the end of a pair of spaced tag axle arms which, in turn, are pivotally mounted to the rear portion of a truck chassis according to a generally known arrangement. Linear reciprocating operating devices, typically hydraulic cylinders, or pneumatic devices are employed to pivot the tag axle system between a raised or stowed position and a lowered or ground-engaging position. The force applied by the tag axle system in support of the load may be varied by controlling the applied pressure.
The pivotal swing frames of the class mount in some fashion from the main longitudinal chassis frame or rail members possibly using a pair of flange members each of which carry a pivot pin member journaled in a bushing or bearings carried in an integral housing with one pin member carrying each of the pivot arms. Such a system which can accurately be removed and replaced from the spaced longitudinal chassis frame or rail members is illustrated and described in co-pending application Ser. No. 09/507,608, filed of even date, entitled "SWING-FRAME ASSEMBLY FOR TAG AXLE", and assigned to the same assignee as the present invention.
Because of the generally high wear nature of the environmental and other circumstances of use for tag axle systems of the class, frequent repairs may be necessary and such may require the dis-assembly or partial dis-assembly of the unit. For this and other reasons, ease of separation and re-assembly of principle parts is a prime concern to users.
One important consideration involves the assembly and re-assembly of the swing frame to the tag torque tube. They must be related in a manner that assures accurate alignment of the torque tube with the permanent wheel axles of the vehicle which is essential for true tacking of the tag wheels. In the past, this has been an involved process requiring the use of large alignment jigs to assure proper placement of the swing arms relative to the torque tube every time the assembly is put together. This is quite time-consuming. U-bolts, or the like, have typically been used to connect the ends of the swing arms to the torque tube. The U-bolts tend to loosen over time and cause misalignment of the system. Thus, these mounts have been found to be difficult to assemble and maintain in proper alignment.
Thus, there remains a definite need for a system and technique to assemble the pivot arms to the torque tube which results in an accurate repeatable alignment of the torque tube with the pivot arms. The system should work as well for subsequent re-assembly as for the original factory assembly.
Accordingly, it is a primary object of the present invention to provide a system and method that results in labor-saving, accurate, repeatable alignment of the torque tube as it is connected to the pivot arms of a pivot frame tag axle assembly.
It is another object of the present invention to provide a system of sub-assemblies which, when assembled together, result in accurate alignment of the torque tube and pivot arms of a pivot frame tag axle assembly without the need for jigs to align the parts when combining the sub-assemblies.
Still another object of the present invention is to provide such a system that will maintain accurate alignment during use.
Further object, advantages and novel features of the present invention will become apparent from the detailed description of the invention, taken in conjunction with the accompanying claims and drawings.